Temperature control system for a fluid under pressure



G/VALVE OPERA T0,?

lg. Z

T. S. SPRAGUE ETAL Filed Feb. 5. 1948 6754M a mama 0m Pk/MARYJ'UP'fl/fflffk smwoA/aY same/1547s:

O I D E 29 ml AffFMP'PATO TEMPERATURE CONTROL SYSTEM FOR A FLUID UNDER PRESSURE- 4JP/B477/VG 75E UUIZET:

lllllllllllllllllllllll IIL April 29, 1952 SUPik/EATEE TS tAMALLY empoms/ws ELEMENT 7778000/9 SJJarague A Berrano M M DOHO/d l NVENTO Rs ATTORNEY Patented Apr. 29, 1952 TEIVIPERATURE. .G ONTR,

A LU D ND L S STE FOR ER PRESSURE Theodore S. Sprague. and BertrandN. McDonald,

Aurora, 111., assignors to Company, New ljolgk,

New-Jersey Application February 3, 1948, SerialNo. 6,008 3- Clainrs, Cl. 122-479) Thisinven-tion relatesto steam generators, and more particularly: to a steam generator associated with a superheater, and to the control" of superheat insuchan installation.

One method of controlling the superheatnof' high pressure superheated steam involves the absorption of excess superheat by heat transfer directly-to afluid of lower temperature ina direct contact attemperator wherein a spray of; water is introduced into the steam. Another method involves a closed surface type ofheat exchanger in which the superheated steam and the cooling liquid areseparated by metallic walls. The use of the. latter type of attemperator is ad-. vantageous in-that it avoids the possibility ofintroducing contaminants into the steam, but it is subject tothe disadvantage of inherent and substantial steam flow-resistance which reduces the pressure at which. the steam is delivered at, a point of use. This-is particularly true in large capacity installations handling large volumes of steam. Such steam flow. resistance is a very substantial factor where the attemperator heat transfer surface elements are of limited extent, as where theyare. placed in a water space of a steam generator.

Itis an object of the invention to provide a superheated steam attemperator of the surface type associated. with a steam generator by such steam fiow connections. and provisions that there is a counterbalancing or compensatory effect on the steam pressure drop incurred as a result of the steam flow. resistance of the attemperator.

More specifically the invention involves. the association of a steam jet aspirator in the regulating bypass conduit. of an attemperator to reduce the static pressure at the steam outlet con nection of the attemperator.

In one practice of the invention a portion of the steam from a first superheater section is conducted through the attemperator and then to a combined aspirator and mixing T forming a juncture with a bypass line in which the remainder of the superheated steam from the first superheater section is conducted directly to a second superheater section. In this T the bypassing steam passes through a Venturi-like section at high velocity, the attemperated steam having its velocity increased by the effect of the bypassing steam. The attemperated steam enters the T forwardly of the Venturi-like section and is mixed with the bypassed steam.

The invention will be described with reference to an embodiment shown in accompanying drawing, in which:

ia. i a oaei i d eale t Showing the combined; steam aspirator and mixing T involved in thelijig. 1 system.

I n th system sh ownin Fig. 1, saturated steam passgsthrough the line l0 from the steam and water druml2 of a steam generator to the inlet header-- I 4: of; a; primary superheater section It. This section involves a bank of spaced tubes dis-. posed transversely of a gas pass and connected for series flow of steam therethrough to the ead r 1.

The superheated steam from header I8 is di-, videdand-proportioned by a bypass valve [9 between; twofiow paths leading to the inlet header 2 9.. of the secondary superheater section 22. One of; these flow paths includes a conduit 24 leadingto; the inlet ofan attemperator 26 which is advantageously disposed in the submerged drum cr -header- 2 8 of thefsteam generator. From the outlet; of the; attemperator the steam cooled therfibyis.- conducted by a conduit 28 to a combined steam aspirator and mixing T indicated generally at 3 0.

The remainder of the steam from the bypass valve I9? is conducted through the bypass conduit SZ-directly to the aspirator and mixing T 3 0; where. thebypassed steam is mixed with the attemperated steam entering through the conduit 29.

The bypassing steam flowing in conduit 32- is directed through nozzle 34 fixed within the T at'its upstream end and having its discharge endin. the-zone of-the lateral port 29' connected tothe conduit 2a. The nozzle increases the velocity ofthe steam with the result that the static pressure thereof at the position of high velocity is substantially reduced from that in conduit. 32. The reduced static pressure thereby developed in the zone surrounding the nozzle outlet thus reduces, the back pressure related to the port. 29. of conduit. 29. As the flow through the steam carrying tubes of the attemperator and its conduit connections is a direct function of the difference in pressures existing at the valve end of conduit 24 and the T port 29', the reduction of pressure at the zone of the port 29 effects a higher flow of steam.

Immediately downstream from the lateral connection or port 29' of the T 39 with the conduit 29 is a Venturi-like tubular section 36, secured as by welding, within the T in alignment with the nozzle 34 and acting to thoroughly merge the attemperated and bypassed steam while the diverging portion of the Venturi tube effects a gradual reduction of steam velocity with an efficient recovery of static pressure.

The mixed steam is conducted from the T 36 through conduit 38 to header 2?! for the second superheater section. This section is formed by a bank of spaced tubes similar to that of section It, the tubes being series connected to discharge steam at final superheat to a superheater outlet header 4!).

The recovery of static pressure is such that the overall steam pressure drop incurred between headers l8 and 20 is less than if the bypassed and attemperated steam streams were merged in a junction fitting without the development of the aspirating effect by the jet action of the bypassed stream.

The bypass valve l9 includes a single valve stem or shaft 42 turnably mounted in the valve walls and in a diaphragm C between branches A and B which lead respectively to the bypass 32 and the attemperator conduit 24. Secured to the valve shaft 42 in the branches A and B are the valve members D and E. They are set 90 apart so that when steam flow is increased through bypass 32, it is decreased through the attemperator, and vice versa. Such proportioning of steam flows is preferably automatically controlled in response to slight variations of final steam temperature from a predetermined value.

In the operation of a steam boiler of the type indicated, the maximum correction of superheating steam temperature by attemperation will be carried out at maximum load at which time the maximum flow of steam through the superheater section will occur, but with the division of steam between conduits 24 and 32 accomplished by valve 19 to direct such an amount through the former conduit that the desired steam temperature at a position following the T 30 results. At low ratings when no attemperation of the low steam flow is desired, the valve l9 will be operated to close off the inlet to conduit 24 and thereby bypass all of the steam through the nozzle 34.

As the pressure drop from inlet header M to outlet header 48 is greatest at high loads, it will be appreciated that the aspirating T is effective in the load range where the pressure drop is most important.

By way of further indication of the steam generator, the drawing shows the lower ends 21 of steam generating .ibes which are in communication with the steam and water drum I2 by the circulators l and any necessary interposed header. Fig. 1 also indicates downcomers l3 leading from the water space of the drum l2. The lower ends of these downcomers are connected to the water drum 28, as indicated at 3|.

What is claimed is:

1. In a steam generator-superheater installation, a steam and water drum, a primary superheater section receiving saturated steam from the drum, a second superheater section receiving steam from the primary section through two flow paths arranged in parallel, a water drum, an indirect type of attemperator in one of said flow paths, the liquid containing portion of said attemperator being the water drum, tubular means connecting said drums into the circulatory system of the generator, the other flow path bypassing the attemperator, valve means variably proportioning the steam flows through said now paths in response to variations in total steam temperature from a predetermined value, and an aspirator at the downstream juncture of the bypass and the other flow path utilizing the higher pressure of the bypassing steam to increase the efiective steam pressure drop through the attemperator 2. In a steam generator-superheater installation, a steam and water drum, a gas heated primary superheater section receiving steam from the drum, a second superheater section receiving steam through two flow paths from the primary superheater section, a water drum of the generator, a steam attemperator in said water drum forming a part of one of said flow paths, the liquid containing portion of said attemperator being the water drum, the other flow path bypassing the attemperator, valve means variably proportioning the steam flows through said paths to maintain a predetermined final steam temperature, and a combined aspirator and mixing T joining said flow paths at a position downstream from the attemperator, said T having a bypass steam nozzle discharging into a Venturitype mixer and having a connection with the flow path leading from the attemperator 3. In a steam generator-superheater installation, a steam and water drum, a primary superheater section receiving saturated steam from the drum, a second superheater section receiving steam from the primary section through two flow paths arranged in parallel, a water drum, an indirect type of attemperator in one of said flow paths, the liquid containing portion of said attemperator being the water drum, tubular means connecting said drums into the circulatory system of the generator, the other flow path lay-passing the attemperator, valve means variably proportioning the steam flows through said flow paths to control steam temperature, and an aspirator at the downstream juncture of the by-pass and the other flow path utilizing the higher pressure of the by-passing steam to increase the efiective steam pressure drop through the attemperator.

THEODORE S. SPRAGUE.

BERTRAND N. MCDONALD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

